The invention provides a closed-loop test system based on digital simulation, which comprises a control unit, a simulation calculation unit and an interface unit, wherein the control unit is used forinputting simulation data of a power system and publishing a control command; the simulation calculation unit is used for calculating an electromagnetic transient process and an electromechanical transient process of the power system; the interface unit is provided with communication interfaces of four types including AI, AO, DI and DO for communication with the outside, and the interface unit isconnected with an external power amplifying device by means of analog signals; during the closed-loop test, an AI/DI port of the interface unit is in communication connection with an external tested device, reads AI/DI data, transmits the AI/DI data to the digital simulation calculation unit for simulation calculation of the electromagnetic transient process and the electromechanical transient process, and transmits AO/DO data obtained through calculation to the interface unit. During the closed-loop test, the closed-loop test system based on digital simulation can conduct simulation calculation of the electromagnetic transient process and the electromechanical transient process, and the test result is precise.